Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$160.75	8.345%	$174.1646	$174.16	$174.15	$174.20
Purchase #2	$62.93	3.868%	$65.3641	$65.36	$65.35	$65.40
Purchase #3	$173.99	4.271%	$181.4211	$181.42	$181.40	$181.40
Purchase #4	$52.74	13.449%	$59.833	$59.83	$59.85	$59.80
Purchase #5	$161.73	4.379%	$168.8122	$168.81	$168.80	$168.80
Purchase #6	$119.71	4.832%	$125.4944	$125.49	$125.50	$125.50
Purchase #7	$165.73	3.505%	$171.5388	$171.54	$171.55	$171.50
7 purchase totals =	$897.58		$946.6282	$946.61	$946.60	$946.60